tests/test-basic.t

hg: make cachedlocalrepo cache appropriate repoview object

Before this patch, 'cachedlocalrepo' always caches "visible" repoview
object, because 'cachedlocalrepo' uses "visible" repoview returned by
'hg.repository()' without any additional processing.

If the client of 'cachedlocalrepo' wants "served" repoview, some
objects to be cached are discarded unintentionally.

    1. 'cachedlocalrepo' newly caches "visible" repoview object
       (call it VIEW1)

    2. 'cachedlocalrepo' returns VIEW1 to the client of it at 'fetch()'

    3. the client gets "served" repoview object by 'filtered("served")'
       on VIEW1 (call this "served" repoview VIEW2)

    4. accessing to 'repo.changelog' implies:
       - instantiation of changelog via 'localrepository.changelog'
       - instantiation of "filtered changelog" via 'repoview.changelog'

    5. "filtered changelog" above is cached in VIEW2

    6. VIEW2 is discarded after processing, because there is no
       reference to it

    7. 'cachedlocalrepo' returns VIEW1 cached at (1) above to the
       client at next 'fetch()'

    8. 'filtered("served")' on VIEW1 at the client side creates new
       "served" repoview again, because VIEW1 is "visible"
       (call this new "served" repoview VIEW3)

    9. accessing to 'repo.changelog' implies instantiation of filtered
       changelog again, because "filtered changelog" is cached in
       VIEW2 at (5), but not in VIEW3 currently used

    10. (go to (7) above)

As described above, "served" repoview object and "filtered changelog"
cached in it are discarded always, even if the repository itself
hasn't been changed since last access.

For example, in the case of 'hgweb_mod.hgweb', "newly caching" occurs,
when:

  - all cached objects are already assigned to another threads
    (in this case, repoview is created in 'cachedlocalrepo.copy()')

  - or, stat of '00changelog.i' is changed from last access
    (in this case, repoview is created in 'cachedlocalrepo.fetch()')

    once changes are pushed via HTTP, this always occurs.

The root cause of this inefficiency is that 'cachedlocalrepo' always
caches "visible" repoview object, even if the client of it wants
another view.

To make 'cachedlocalrepo' cache appropriate repoview object, this
patch adds additional filtering on the repo object returned by
'hg.repository()'. It is assumed that initial repoview object should
be already filtered by expected view.

After this patch:

  - 'filtered("served")' on VIEW1 at (3)/(7) above returns VIEW1
    itself, because VIEW1 is now "served", and

  - VIEW2 and VIEW3 equal VIEW1

  - therefore, "filtered changelog" is cached in VIEW1, and reused
    intentionally

Create a repository:

  $ hg config
  defaults.backout=-d "0 0"
  defaults.commit=-d "0 0"
  defaults.shelve=--date "0 0"
  defaults.tag=-d "0 0"
  devel.all-warnings=true
  largefiles.usercache=$TESTTMP/.cache/largefiles (glob)
  ui.slash=True
  ui.interactive=False
  ui.mergemarkers=detailed
  ui.promptecho=True
  $ hg init t
  $ cd t

Make a changeset:

  $ echo a > a
  $ hg add a
  $ hg commit -m test

This command is ancient:

  $ hg history
  changeset:   0:acb14030fe0a
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     test
  

Verify that updating to revision 0 via commands.update() works properly

  $ cat <<EOF > update_to_rev0.py
  > from mercurial import ui, hg, commands
  > myui = ui.ui()
  > repo = hg.repository(myui, path='.')
  > commands.update(myui, repo, rev=0)
  > EOF
  $ hg up null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ python ./update_to_rev0.py
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg identify -n
  0


Poke around at hashes:

  $ hg manifest --debug
  b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644   a

  $ hg cat a
  a

Verify should succeed:

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 1 changesets, 1 total revisions

At the end...

  $ cd ..